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APPENDIX                                     309

or cone, sulphuric acid, can be adopted in the majority of cases
with good results, and has many advantages over the old
method of passing hydrochloric acid gas into a mixture of the
alcohol and acid until saturated. Read Notes on Prep. 15,
p. 247.


Acetophenone.—The " Friedel-Crafts' reaction," of which
this preparation is a type, consists in the use of anhydrous
aluminium chloride for effecting combination between an
aromatic hydrocarbon or its derivative on the one hand, and a
halogen (Cl or Br) compound on the other. The reaction is
always accompanied by the evolution of hydrochloric or hyclro-
bromic acid, and the product is a compound with A1C13, which
decomposes and yields the new substance on the addition of
water. This reaction has been utilised, as in the present case,
(r) for the preparation of ketones, in which an acid chloride
(aliphatic or aromatic) is employed,



Cflllfl + Cl.CO.CfiTTs = CflHrt.CO.CflHe + TICK


If a substituted aromatic hydrocarbon is used, the ketone
group then enters the para-position, or, if this is occupied, the
ortho-position. Substituted aromatic acid chlorides may also
be used, and if the acid is dibasic and has two carboxyl chloride
groups, two molecules of the aromatic hydrocarbon may be
attached. If phosgene is used with two molecules of benzene,
bemophenone is obtained,

2CCHG + C12CO = C6HB.CO.C0H0 + 2HC1.


(2) This reaction may be modified by decreasing the propor-
tion of the hydrocarbon, and an acid chloride is then formed.,

:(.ntj H- cicoci = COHB.COCI + nci.
Benxoyl chloride,